This invention relates to accumulating conveyors, and more particularly to a control system for an accumulating conveyor which is operable to advance loads in a singulated manner along the conveyor system.
An accumulating conveyor generally includes a series of zones which can be selectively controlled to allow articles being conveyed to accumulate in a selected area of the conveyor. Examples of control systems for providing certain functions of an accumulating conveyor are disclosed in Hall U.S. Pat. No. 5,225,558 issued Jul. 20, 1993 and Hall U.S. Pat. No. 5,285,887 issued Feb. 15, 1994.
Methods for operating accumulating conveyors have been well established over the years. One such method is known as train release, which is operable to run multiple zones simultaneously regardless of whether or not there is a load on the zone. Train release is typically used near the discharge end of an accumulating conveyor to provide a large quantity of objects in rapid succession. While this method of control provides a high throughput of loads on the conveyor, it is disadvantageous in that there is an overall loss of control of the conveyor. Further, train release typically enables a single zone to carry multiple loads, which is undesirable in certain circumstances when it is necessary to ensure there is only a single load per zone, such as when loads are being weighed, sorted, counted, packaged or subject to any other operation to be carried out on a single load.
To ensure each zone carries only a single load, it is known to control an accumulating conveyor to provide singulated release of loads. In a singulated release control, the conveyor zones are controlled such that a load is discharged from one zone only when the immediately adjacent downstream zone is empty. Singulated release control is generally used to fill accumulating conveyors and to operate as a normal transport mode. This type of control is a very straightforward approach which can be accomplished using air logic, mechanical switches, combinations of clutches and brakes, or individually powered conveyor sections. While conventional singulated release is operable and generally satisfactory, it is disadvantageous in that the conveyor throughput is relatively low. At any given time in the transport mode, less than half of the total length of the conveyor is occupied since adjacent loads will be separated by a gap at least equal to the length of each conveyor zone.
It is an object of the present invention to provide an improved singulated release control for an accumulating conveyor to increase the throughput of the conveyor. It is a further object of the invention to provide an improved singulated release control which increases throughput by minimizing the gap between adjacent loads. Another object of the invention is to provide such a conveyor control which is simple in its operation and easy to implement for use in conventional conveyor control systems.
In accordance with the invention, a conveyor system for transporting a series of loads includes a series of conveyor zones which includes at least an upstream conveyor zone and a downstream conveyor zone. A drive arrangement is interconnected with each conveyor zone for operating each conveyor zone to advance loads along the conveyor system. The invention contemplates a control arrangement interconnected with each drive arrangement, with the control arrangement being operable on each drive arrangement to initially operate the upstream and downstream conveyor zones to advance adjacent first and second loads thereon. The control arrangement is further operable to stop operation of the upstream conveyor zone when the first load is discharged from the upstream conveyor zone and is supported by the downstream conveyor zone and the second load is supported by the upstream conveyor zone, to maintain the second load stationary. The control arrangement is further operable to maintain operation of the downstream conveyor zone to advance the first load relative to the second load on the downstream conveyor zone, and to thereafter resume operation of the upstream conveyor zone when the first load approaches the downstream end of the downstream conveyor zone, to simultaneously advance the first and second loads on the downstream and upstream conveyor zones, respectively. Each conveyor zone includes a downstream sensor adjacent its downstream end. The control arrangement is responsive to inputs from the sensors, and preferably includes a control module for each conveyor zone to control the drive arrangement interconnected with the conveyor zone. The control arrangement is preferably operable to stop operation of the upstream conveyor zone when the first load is discharged from the upstream conveyor zone and the subsequent load on the upstream conveyor zone reaches the downstream end of the upstream conveyor zone, in response to inputs from the sensor of the upstream conveyor zone. The control arrangement is further operable to resume operation of the upstream conveyor zone when the first load approaches the downstream end of the downstream conveyor zone, in response to an input from the sensor of the downstream conveyor zone.
The invention further contemplates a method of controlling a conveyor having adjacent upstream and downstream conveyor zones for advancing a series of loads, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.